CMFAS CGI Marine Cargo & Hull Insurance question: own right rather than absorbed into ordinary non-marine property cover

Why is marine insurance examined as a class in its own right rather than absorbed into ordinary non-marine property cover?

• A It is governed by long-established marine law and international clauses, with concepts like general average
• B It is the only class of general insurance that never requires the insured to hold insurable interest at any stage
• C It is written exclusively on annual time policies, with no voyage or transit cover available to shippers
• D It is the cheapest class of commercial cover and is therefore singled out for separate study by insurers